For automobile windows, usually safety glass consisting of glass plates laminated together with a polybutyral film is used in order to prevent scattering of shattered glass when window glasses (windshields) are broken. However, polybutyral is inferior in heat resistance and, therefore, cannot be laminated with a heat ray reflection layer or layers comprising a metal or a metallic compound and thus it is difficult to provide safety glass with heat-ray-reflection property.
Although various resins have been studied in search of better replacements of polybutyral, no material satisfactory in transparency, heat resistance, strength and non-occurrence of interference fringe due to polarization of light has not yet been developed.
We conducted an extensive study in consideration of the above-described problems and found a laminating material for safety glass having excellent characteristics.